A fieldbus is a specific type of local area network (LAN) that is used to monitor or control one or more pieces of production equipment. The term "Fieldbus" generally refers to an all-digital, two-way communication system that connects control systems to instrumentation. A fieldbus network comprises a plurality of digital devices and control/monitoring equipment that are integrated to provide I/O and control for automated processes. A fieldbus network is typically used in industrial and/or process control applications, such as a factory or manufacturing plant. The physical devices in a fieldbus system are connected by the fieldbus. One example of a fieldbus network is the Fieldbus Foundation fieldbus network.
Foundation Fieldbus, which is the serial communications network created by the Fieldbus foundation, specifically targets the need for robust distributed control in process control environments. Devices connected by a Foundation Fieldbus exchange data between themselves, and thus control a fieldbus process. Devices are given the opportunity to communicate data by a token passing scheme controlled by a device referred to as the "Link Active Scheduler" or LAS (a device used to schedule communication traffic).
The components of a Foundation Fieldbus Network are as follows:
1) Link
2) Devices
3) Blocks and Parameters
4) Linkages
5) Loops
6) Schedule
Fieldbus networks may contain one of four types of devices, these being temporary devices, field devices, interface devices, and monitor devices. Temporary devices are devices attached to one of four network addresses reserved for temporary or visitor use. Temporary devices are typically used for configuration and troubleshooting. Field devices are devices that typically comprise function block application processes or, in other words, devices that perform the I/O and control that automates the plant or factory. All field devices arc given a permanent address by the system manager when they are attached to the network. Interface devices perform data display and other interface functions for field devices. Like field devices, interface devices are assigned a permanent address, but interface devices do not necessarily contain function block application processes. Finally, monitor devices are devices that are able to listen to network traffic but are not permitted to transmit onto the network. Monitor devices receive no address when attached to the network, and the other network devices are unaware of the monitor's presence.
As mentioned above, a field device generally comprises one or more function block application processes, referred to as function blocks. A function block comprises an algorithm and one or more parameters associated with the algorithm. Function blocks model field device functions, such as analog input (AI) functions and PID (Proportional Integral Derivative) control loop functions, among others. The function block model provides a common structure for defining function block inputs, outputs, algorithms and control parameters. This structure simplifies the identification and standardization of characteristics that are common to function blocks.
The function block model includes associated standardized definitions used to support function blocks. These definitions include the Object Dictionary (OD) and the Device Description Language (DDL). These definitions support application processes in the definitions and description of their network visible objects, such as function blocks and their parameters.
Each physical device performs a portion of the total system operation by implementing one or more application processes. Application processes perform one or more time-critical functions, such as providing sensor readings or implementing one or more control algorithms. As noted above, these field device functions are modeled by function blocks. The operation of the various function blocks is coordinated through configuration of their external communications, execution schedules, and operating parameters.
Physical devices in a fieldbus system are interconnected by a fieldbus network. Fieldbus networks may be comprised of one or more link segments interconnected by bridges. Communication between physical devices is provided by physical layer and data link layer protocols. Intervening bridges forward messages transparently between links.
A fieldbus network utilizes a four layered communication stack or four layer protocol, including a physical layer, a data link layer, and application layer that is divided into an access sublayer and a messaging sublayer. Transfer of information between field devices is provided by the physical layer and data link layer protocols. The physical layer specifies how signals are sent, the fieldbus data link layer (FDL) specifies how the network access is shared and scheduled among devices, and the application layer defines the message formats available to applications for the exchange of commands. Communications between application processes in the field devices occurs through the application layer protocols. The application layer is divided into two sublayers, an upper sublayer, defined by the Fieldbus Messaging Specification (FMS), that provides services to application processes, and a lower sublayer, known as the Fieldbus Access Sublayer (FAS), that maps FMS services onto the underlying capabilities of the data link layer.
In fieldbus networks, information is transmitted along the fieldbus in discrete segments commonly referred to as packets. Packets are passed between the field devices connected to the network. Each packet may contain FDL information, FAS information, and FMS information corresponding to the various architectural layers used in the fieldbus implementation.
System management is used in fieldbus networks to coordinate the operation of the various devices in a distributed fieldbus system. System management functions include node address assignment for devices, application clock synchronization, distributed application scheduling across the segment, and support for locating application tags. System management provides the facilities to bring new devices on the segment to an operational state and to control the overall system operation. System management uses FMS to remotely access management information within a device and to directly access the data link layer to carry out its other functions. A single system management entity exists in each device for each data link segment connected to the device. The entity comprises user applications and a system management kernel. The kernel provides a network coordinated and synchronized set of functions.
A fieldbus configuration utility is generally used to create a fieldbus application. The fieldbus configuration utility is used to create a schedule for the fieldbus devices to control operation of the fieldbus devices. However, current fieldbus configuration utilities do not provide a simplified manner for creating a fieldbus configuration.
Applicants are aware of a fieldbus configuration utility available from SMAR. The SMAR fieldbus configuration utility provides a mechanism for connecting function blocks and editing parameters. However, the SMAR fieldbus configuration utility does not display input and output parameters on the function block diagram, and thus is not intuitive and user friendly. The SMAR fieldbus configuration utility also does not provide for scheduling. The SMAR fieldbus configuration utility does not include device descriptions, and thus does cannot determine arbitrary data types. The SMAR fieldbus configuration utility further does not provide a method for configuring trends and alerts and does not classify parameters in any way.
Therefore, an improved fieldbus configuration utility is desired which provides an improved user interface and simplified development for fieldbus applications.